Has anyone ever attempted to use an inductive pickup type sensor to determine engine RPM? Of all the sensors in a car, I find this one to be one of the more troublesome to deal with. Cars have lots of EM noise under the hood already and the signals going to the ECU for the tach are some sort of multiplexed digital, which I'm not going to attempt to figure out. I was looking at something like this:
but again, there's the noise issue and I don't know what quality of signal might be. I don't want to re-invent the wheel and I know that there's already devices that wrap around the spark plug or injector wires to count pulses and get RPM from that (they do it in dyno shops) but I don't want to buy some 500 dollar proprietary thing when a simple breakout board will do the same job.
Any suggestions?
proximity sensors are inductive sensors I think and are widely used. They come in some small sizes too.
But a prox is meant for a different sort of application, like when a piece of metal approaches the prox, it will flip on for example. I use them at work. I'm not aware of using them to detect current spikes in adjacent stationary wires. Can they do that as well?
It occurred to me that I could lay a single wire down parallel to the spark plug wire on 1 cylinder and then run the signal that's induced on the wire through an FHT to get the frequency I'm after (something between 0 and 3500/min probably since the spark plug only fires once every 2 rotations). This to me seems very hackish and mickey mouse though. I'd rather use a discrete component meant for this purpose than have to fashion my own pickup. Something like an amp clamp would be great except amp clamps aren't designed to be used this way but the principle is sound.